| 摘要 |
PURPOSE:To reduce the number of lines of transmission line by using a common signalling channel for calling signal as a transmission line in addition to a channel. CONSTITUTION:A signal conversion circuit 22 on the exchange 2-side converts a signal from a slave telephone set 3 to a calling signal to a master telephone set 1. When the exchange 2 ends the connection to the master telephone set 1, the circuit 22 on the exchange 2-side transmits a signal corresponding to the number of the slave telephone set 3 which is calling to a signal line 5. On the side of the slave telephone set 3 on caller-side, the connection is completed by a signal conversion circuit 32, a signal control circuit 31, and a switching circuit, etc. Thus the two-way call between the calling slave telephone set 3 and the master telephone set 1. In such a way, by using the common signalling channel for calling signal as a transmission line in addition to the channel, the number of lines of transmission line can be decreased. |
